Resolving color differences of comet 41P/Tuttle-Giacobini-Kresák

Abstract

Three different measurement campaigns have resulted in three drastically different sets of color measurements of Comet 41P/Tuttle-Giacobini-Kresák, ranging from a strongly red to a strongly blue color. Although the color slope is normalized to the wavelength range between the filters used, this only serves to partially normalize the resulting color, as the reflectance of cometary dust has a very strong dependence on particle absorption, which may change significantly over the wavelength range of measurement. We demonstrate that the different measurements are physical and are consistent with real materials; for example, we are able to reproduce the color measured during one epoch in which both strong blue and red color slopes were measured almost simultaneously in different filter sets with the mineral dust pyroxene. Such measurements with different filter sets serve as an additional constraint in modeling dust properties.

Photometric BVR observations of comet C/2012 J1 (Catalina) before and after perihelion

“…Zubko et al (2020) indicate that only gas-poor comets can exhibit negative polarization at small phase angles. Another important factor is that the contribution from gas emission is effectively attenuated when the photometric flux is measured at small apertures (Luk'yanyk et al 2020), such as the values used in this study.…”

Polarimetric analysis of STEREO observations of sungrazing Kreutz comet C/2010 E6 (STEREO)

“…The often-used explanation of surrounding gas causing the dampening of the polarimetric response is unlikely to be valid for this feature due to the close proximity to the Sun, where strong dissociation effects mean most gas species are very short-lived (e.g. Biesecker et al 2002 ;Luk'yanyk et al 2020 ). Biesecker et al ( 2002 ) has shown that some species, such as NaI, may be detected as close as 7 R , with others, like Ly α, appearing even closer to the Sun, but neither of those would be detected by the COR2 coronagraph.…”